The present invention relates to polysiloxane derivatives which have desirable electronic properties. More particularly, it relates to polysiloxanes in which at least one of the silicons is substituted with multiple oligooxyethylene side chains.
Lithium batteries are particularly useful in connection with computers because, among other things, they deliver high levels of power per unit weight. As the technology advances for electrically powered automobiles, there has been some thought of using lithium based batteries for that application as well.
However, most existing lithium batteries contain a liquid such as polyethylene oxide that acts as an electrolyte. If such batteries were to be used in automobiles there would be some risk that an accident (or another event) might cause a leak, with resulting safety and environmental concerns.
For this reason, there has been some thought of using a solid electrolyte with a lithium-based battery system. While polyethylene oxide is a sufficiently conductive material as a liquid, its conductivity in solid form is too low to be practical for this application.
One group tried preparing a polysiloxane derivative in which methylated silicons in the polysiloxane chain were each further substituted with a single oligooxyethylene side chain. See D. Fish et al., 20 Brit. Poly. Journ. 281-288 (1988). The disclosure of this publication and of all other publications referred to herein are incorporated by reference as if fully set forth herein. This created a material that was tried as an electrolyte. Unfortunately, the material was not conductive enough to be commercially competitive.
H. Allcock et al., 29 Macromol. 7544-7552 (1996) proposed polyphosphazenes bearing branched and linear oligoethyleneoxy side groups as solid solvents for ionic conduction. However, certain properties of these materials led them to be less than optimal for use in connection with lithium automotive batteries.
Thus, it can be seen that a need still exists for an improved solid electrolyte conductors for use with lithium-based batteries.
In one aspect, the invention provides compounds containing the following moiety: 
wherein each of R1 and R2 is individually selected for each n and is xe2x80x94CH2CH2CH2xe2x80x94Oxe2x80x94(CH2CH2O)mxe2x80x94; wherein m is individually selected for each R1 and R2 and each n and is at least 2 and less than 100 (preferably 3 to 20); and n is at least 1 (preferably at least 2) and less than 1000 (preferably 15-100). In one form, m is the same for all R1 and R2 and all n""s.
In another aspect, the invention provides compounds containing the following moiety: 
wherein mxe2x80x2 and mxe2x80x3 are each individually selected and are each at least 2 and less than 100 (preferably 3 to 20); and n is at least 1 (preferably at least 2) and less than 1000 (preferably 15-100). In one form, mxe2x80x2 and mxe2x80x3 are the same as each other, and are the same for all n""s.
The invention also provides compounds containing the following moiety: 
wherein mxe2x80x2 and mxe2x80x3 are each individually selected and are each at least 2 and less than 100 (preferably 3 to 20); and n is at least 1 (preferably at least 2) and less than 1000 (preferably 15-100). In one form, mxe2x80x2 and mxe2x80x3 are the same as each other, and are the same for all n""s.
In still another aspect, the invention provides compounds containing the following moiety: 
wherein mxe2x80x2, mxe2x80x3, mxe2x80x2xe2x80x3, and mxe2x80x3xe2x80x3 are each individually selected for each n and each is at least 2 and less than 100 (preferably 3 to 20); and n is at least 1 (preferably at least 2) and less than 1000 (preferably 15-100). In one form, mxe2x80x2, mxe2x80x3, mxe2x80x2xe2x80x3, and mxe2x80x3xe2x80x3 are the same for all n""s.
In still another aspect, the invention provides compounds containing the following moiety: 
wherein mxe2x80x2, mxe2x80x3, mxe2x80x2xe2x80x3, and mxe2x80x3xe2x80x3 are each individually selected for each n and each is at least 2 and less than 100 (preferably 3 to 20); and n is at least 1 (preferably at least 2) and less than 1000 (preferably 15-100). In one form, mxe2x80x2, mxe2x80x3, mxe2x80x2xe2x80x3, and mxe2x80x3xe2x80x3 are the same for all n""s.
These moieties can be part of materials that are entirely polysiloxane, or they can be linked with other organic or inorganic materials. Preferably, such moieties are terminated with an OH or OSiMe3 group, but may also be terminated with a wide variety of terminus groups linked to the chain Si or O, such as branched or unbranched alkyl having less than 30 carbons, alkoxy having less than 30 carbons, alkyl silyl having less than 30 carbons, arylalkyl having less than 30 carbons, and aryl having less than 30 carbons.
Particularly with respect to the first class of such compounds it has been learned that oxygen content of ten to twelve oxygens for at least one n is highly preferable from a conductivity standpoint. It has also been learned that where a single n contains multiple oligooxyethylene branches, the branches can be tied together at both ends (e.g. by a crown ether connection to form a cyclic compound xe2x80x94CH2CH2 linkage).
In another aspect, the invention provides a compound of the formula R1R2SiCl2; wherein R1 is xe2x88x92CH2CH2CH2xe2x80x94Oxe2x80x94(CH2CH2O)mxe2x80x2xe2x80x94T; wherein R2 is xe2x80x94CH2CH2CH2xe2x80x94Oxe2x80x94(CH2CH2O)mxe2x80x3xe2x80x94T; wherein mxe2x80x2 and mxe2x80x3 are each individually selected and are each at least 2 and less than 100 (preferably 3 to 20); and wherein T is individually selected for R1 and R2 and are selected from the group consisting of hydrogen, halogen, alkyl having less than 30 carbons, alkyl silyl having less than 30 carbons, arylalkyl having less than 30 carbons, and aryl having less than 30 carbons. One preferred T group is methyl.
In another aspect the invention provides a method of making such polysiloxane xe2x80x9ccombxe2x80x9d polymers by polymerizing multiple R1R2SiCl2 molecules in the presence of water. The term xe2x80x9ccombxe2x80x9d is used because the side chains make the molecule appear somewhat like a hair comb when the molecule is depicted in written form.
Our compounds were tested for conductivity. They had surprisingly high conductivity, while retaining a number of important characteristics that are desirable with respect to automotive batteries.
The objects of the present invention therefore include providing:
(a) compounds of the above kind which are solids;
(b) compounds of the above kind which are highly electrically conductive;
(c) intermediate compounds useful in making the above compounds; and
(d) efficient methods of making such compounds.
These and still other objects and advantages of the present invention will be apparent from the description which follows. The following description is merely of the preferred embodiments. The claims should therefore be looked to in order to understand the full scope of the invention.